Recently Released Special Editions
Systematic Micaceous Minerals
Not all micaceous looking minerals fall in the MICA group of phyllosilicate minerals. Many of the other silicates appear micaceous but are not. We'll have a look at some of these minerals and hopefully explain the difference. Take a look at our article on Mica and Other Micaceous Minerals.
Vermiculite
- Sold
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- Locality
- Iron mine, Kovdor Massif, Kola Peninsula, Russia
- Formula
- Mg0.7(Mg,Fe3+,Al)6(Si,Al)8O20(OH)4·8H2O
- Availability
- Sold
- Size
- 8 x 6 x 1 cm - Sm Cabinet
Phyllosilicate - Monoclinic - Not a Mica group member. But is micaceous. A member of the Montmorillonite-Vrmiculate group with 2:1 layering, meaning there are two (T) tetrahedral layers with an (M) octahedral layer in between. There is no (I) interlayer and the 2:1 layers are instead held together by weak Van der Waals bonds.
Requires Biotite, Chlorite, Hornbelnd and Serpentines to form. Vermiculite contains so much water it will exfoliate when burned.
This is a nice cleavage plate.
Vermiculite
- Formula
- Mg0.7(Mg,Fe3+,Al)6(Si,Al)8O20(OH)4·8H2O
- Crystal System
- Monoclinic
- Crystal Habit
- Lamellar, Scaly
- Cleavage
- Perfect, None, None
- Luster
- Vitreous - Dull
- Color
- colorless, green, gray white, yellow brown
- Streak
- greenish white
- Class
- Monoclinic - Prismatic
- Fracture
- Uneven
- Hardness
- 1.5-2
- Collection
- Phillips Collection
- Mineralpedia
- View Vermiculite
- On Dakota Matrix
- Previously Sold Vermiculite
- On Dakota Matrix
- Other Available Vermiculite
- WebMineral
- View Vermiculite
- Mindat
- View Vermiculite
Zinnwaldite
- Sold
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- Locality
- Zinnwald, Erzgebirge, Bohemia, Czech Republic
- Formula
- KLiFe2+Al(AlSi3)O10(F,OH)2
- Availability
- Sold
- Size
- 4 x 2 x 0.6 cm - Miniature
Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. A transitional member on the Siderophyllite-Polylitionite join.
Just a small specimen.
Zinnwaldite
- Formula
- KLiFe++Al(AlSi3)O10(F,OH)2
- Crystal System
- Monoclinic
- Crystal Habit
- Pseudo Hexagonal, Micaceous, Platy
- Cleavage
- Good, None, None
- Luster
- Vitreous - Pearly
- Color
- light brown, silvery white, gray, yellowish white, greenish white
- Streak
- white
- Class
- Monoclinic - Prismatic
- Fracture
- Uneven
- Hardness
- 3.5-4
- Collection
- Phillips Collection
- On Dakota Matrix
- Previously Sold Zinnwaldite
- On Dakota Matrix
- Other Available Zinnwaldite
- WebMineral
- View Zinnwaldite
- Mindat
- View Zinnwaldite
